Method of inhibiting corrosion



March 13, 1962 E. R. BLAIR ET AL 7 3,025,184

METHOD OF INHIBITING CORROSION Filed Jan. 51, 1958 /A////5/T/A/6 METALsu Poer //V///B/77N6 META L SURF/46E 70 BE PROTECTED JUPPOET EOLLape/Am;

FUL (RUM I NVENTORS E/IPL R BAA/P PAUL lMf/APDY BY Q Q M A TTOE/VEKS3,025,184 METHOD OF'EJH'IBIG CURRQSIUN Earl R. Blair-,Oaklarkyand PaulW. Hardy, Barrington, lillL, assignors to American Can (Iompany, NewYork, N.Y., a corporation of New Jersey Filed Jan. 31, 1958, Ser. No.712,298 3 Claims. (Cl. 117-131) The present invention relates to amethod of inhibiting atmospheric corrosion or rusting of black iron.More particularly, this invention relates to a method of depositing atrace amount of a particular metal onto the surface of black iron inorder to inhibit rusting of the black iron.

Low carbon sheet steel, known in the art as black iron or black plate,is readily susceptible to atmospheric oxidation, commonly known asrusting. For many end uses of black iron, there is a considerable lapseof time between its fabrication by the steel mills and its receipt anduse by the end user. During at least a portion of this time lapse, theblack iron is subjected to conditions conductive to the formation ofrust (high relative humidity and temperature) on its surface.

For many operations, this rust must be removed before the black plate issuitable for the operation intended. Such rust removal requires time andequipment which obviously add expense to the operation.

It is, therefore, an object of the present invention to provide a methodfor treating the surface of black plate during or after its fabricationat the steel mills which will inhibit rusting of the plate at leastuntil its end use.

Yet another object is to provide a method of the character describedwhich is quick and easy to effect, inexpensive and requires simple,inexpensive equipment.

Numerous other objects and advantages of the invention will be apparentas it is better understood from the following description which is of apreferred embodiment thereof.

Referring to the drawing, the single FIGURE in the drawing is aprospective view of one form of apparatus useful in carrying out theinstant invention.

The present invention is based upon the discovery that a thin, invisibledeposit of tin or lead on the surface of black plate will effectivelyinhibit atmospheric oxidation, or rusting, of the black plate surface.This phenomenon was first discovered with tin or lead electrolyticallydeposited from solution onto the surface of black iron. However, such aprocedure for obtaining the desired result was deemed impracticablesince it required extensive electrochemical equipment such as liquidholding tanks, electric current supply, drying apparatus, etc. Uponfurther investigation of this phenomenon, we discovered that the samedesired results could be achieved merely by rubbing a solid element oftin or lead onto the black iron surface to be protected.

By means of this discovery, effective corrosion protection of black ironmay be accomplished very simply during a steel rolling operation asperformed in a steel mill during the fabrication of black plate. Toperform this operation, a solid element of tin or lead is mounted at aconvenient place in the path of travel of the sheet steel during therolling thereof so that the sheet steel rubs against this elementwhereby the corrosion inhibiting metal is abraded onto or applied to thesteel surface. Since, as indicated previously, it is necessary merely toa'orade inhibiting metal against the steel surface, no special provisionfor heating the inhibiting metal or steel surface is necessary. Thus,the abrading operation will take place at any temperature substantiallybelow the melting point of the inhibiting metal, tin or lead, preferablyat room temperature. The element may take the form of a stationary baror block, or of a fixedly mounted roller or cylinder adapted to rotateat a velocity, i.e. di-

rection and/or speed, different from that of the moving steel sheet.

Tobe effective, the entire black iron surface must be rubbed with thecorrosion inhibiting metal. The amount of inhibiting metal depositedonto the surface to be protected is so small as to be invisible. At anyrate, the quantity of inhibiting metal amounts to not more than 1X10lbs. per square inch of surface treated.

It is not known whether or not the inhibiting metal is uniformly andcontinuously applied over the black iron surface. Because of the almostinfinitesimal amount of inhibiting metal applied to the surface, noadequate tests for such uniformity and continuity have been found.However, by virtue of its mode of application, i.e. merely rubbing theinhibiting metal over the surface to be treated, it is believed that thedeposit of inhibiting metal is not uniform or continuous since nospecial precautions or conditions were followed to achieve this result.

The inhibiting metal must be free of oxide. Experiments have shown thatrubbing a black plate surface with inhibiting metal having an oxide filmthereon produces no corrosion inhibition. However, it is obvious thatinitially the solid element of inhibiting metal may have an oxidecoating thereon which is abraded off or removed after a short period ofrubbing contact with the black iron surface; whereupon pure inhibitingmetal will thereafter be deposited on the surface to be protected.

Surprisingly, only tin and lead were found to have a corrosioninhibiting effect when applied in accordance with the instant invention.Other metals which are known to form a protective coating on steel weretried and had no corrosion inhibiting effect whatsoever. Among the othermetals tried and found ineffective were antimony, aluminum, nickel andtitanium. The reason for this difference in action between the efiectiveinhibiting metals and the non-effective metals is not understood.Although not wishing to be bound by any particular theory, the closestexplanation is that the particular electronic configuration of the atomsof tin and lead in relation to steel causes these metals to be effectivecorrosion inhibitors; whereas the other, non-effective metals have adifferent electronic configuration causing them to be non-operable.

It is thought that the invention and many of its attendant advantageswill be understood from the foregoing description, and it will beapparent that various changes may be made in the steps of the methoddescribed and their order of accomplishment without departing from thespirit and scope of the invention or sacrificing all of its materialadvantages, the method hereinbefore described being merely a preferredembodiment thereof.

We claim:

1. A method of treating a black iron surface to inhibit rusting thereofcomprising, passing said surface along a predetermined path of travel,placing a solid element of a substantially pure inhibiting metalselected from the group consisting of tin and lead in said path oftravel, and abrading said surface against said element at a temperaturesubstantially below the melting point of said inhibiting metal duringthe travel of said surface to provide said surface with a thin invisibledeposit of said inhibiting metal in an amount of up to 1x10 lbs. persquare inch of said surface.

2. A method of continuously treating the surface of a. fiat sheet ofblack iron to inhibit rusting thereof comprising, passing said sheetcontinuously along a predetermined path of travel, placing a solidelement of a substantially pure inhibiting metal selected from the groupconsisting of tin and lead along said path of travel, and abrading saidsurface against said element at a temperature substantially below themelting point of said inhibiting metal during the travel of said sheetto provide said surface with a thin invisible deposit of said inhibitingmetal in an amount of up to 1x10 lbs. per square inch of said surface.

3. The method set forth in claim 2 wherein said solid element ofinhibiting metal is fixedly positioned along said path of travel.

References Cited in the file of this patent UNITED STATES PATENTS

1. A METHOD OF TREATING A BACK IRON SURFACE TO INHIBIT RUSTING THEREOFCOMPRISING, PASSING SAID SURFACE ALONG A PREDETERMINED PATH OF TRAVEL,PLACING A SOLID ELEMENT OF A SUBSTANTIALLY PURE INHIBITING METALSELECTED FROM THE GROUP CONSISTING OF TIN AND LEAD IN SIAD PATH OFTRAVEL, AND ABRADING SAID SURFACE AGAINST SAID ELEMENT AT A TEMPERATURESUBSTANTIALLY BELOW THE MELTING POINT OF SAID INHIBITING METAL DURINGTHE TRAVEL OF SAID SURFACE TO PROVIDE SAID SURFACE WITH A THIN INVISIBLEDEPOSIT OF SAID INHIBITING METAL IN AN AMOUNT OF UP TO 1X10-6 LBS. PERSQUARE INCH OF SAID SURFACE.